Device interaction may be based upon proximity detection in which the presence of a communication device is initially determined and the proximity of the communication device is then tracked. In some instances, proximity detection may be accomplished in a seamless manner without user interaction or dependence upon application status.
Following the identification of the presence of a communication device, subsequent tracking of the proximity of the communication device would advantageously consume relatively low amounts of power and have relatively low latency in regard to the proximity detection. In order to reduce power consumption or to allow activity to be supported on another physical channel in instances in which device interaction is supported by Bluetooth, a Bluetooth basic rate (BR)/enhanced data rate (EDR) link that is established between a pair of communication devices may be configured to operate in a sniff mode. In the sniff mode, one of the communication devices is designated the master and the other communication device is designated the slave with the duty cycle and the slave's activity in the piconet being reduced. In an instance in which the slave device is in an active mode on an asynchronous connectionless (ACL) logical transport, the slave device may listen in every ACL slot for signals from the master device unless the link is treated as a scatternet link or as absent due to hold mode. In the sniff mode, however, the time slots in which a slave device listens for signals from the master device are reduced, since the master device shall only transmit signals to the slave device in specified time slots. As shown in FIG. 1, and as described by the Bluetooth specification version 4.0, the sniff mode may define a plurality of sniff anchor points at which the master device may commence transmission of signals to the slave device. The sniff anchor points may be spaced regularly with an interval of Tsniff. In an instance in which sniff sub-rating is enabled by the link manager, the communication devices may alternate between sniff mode and sniff sub-rating mode, with the sniff sub-rating mode allowing a communication device to utilize a reduced number of anchor points.
While the sniff mode reduces the power consumption required for proximity detection, sniff mode increases latency associated with proximity detection. Conversely, the latency associated with proximity detection may be reduced by more frequently or even continuously tracking the communication device, but at the expense of increased power consumption.